1. Technical Field
The present invention relates to a facsimile machine.
2. Background Art
Recently, facsimile machines should be constructed in line with ITU-T Recommendation. ITU-T Recommendation T.30 defines standard and non-standard procedures with respect to protocol signal transmission performed prior to image data transmission.
The standard procedure is a requisite to all facsimile machines, but the non-standard procedure is not. Therefore, the non-standard procedure may be performed as additional functions of the facsimile machine.
Between two conventional facsimile machines, a protocol signal for the standard procedure which is provided with a functional bit to perform a function of the facsimile machine defined in standard procedure is transmitted to one facsimile machine from another facsimile machine. Other functions which are not defined in the standard procedure are executed upon transmission of functional bits included in a protocol signal for the nonstandard procedure.
Specifically, if ITU-T recommends to transmit to a third party a functional bit which represents availability of fine mode reception (vertical resolution=7.7 l/mm) in the protocol signal for the standard procedure, the facsimile machine transmits such a functional bit to the third party during the standard procedure and does not transmit it during the non-standard procedure.
However, this type of facsimile machine has following problems:
Contents of the ITU-T Recommendation will change with progress of functions of the facsimile machines. Thus, even if today's ITU-T Recommendation does not include a functional bit for superfine (vertical resolution is 15.4 lines/mm) mode in the standard procedure, tomorrow's ITU-T Recommendation might include it.
If new ITU-T Recommendation issues, then a facsimile machine manufactured thereafter transmits protocol signal which has a functional bit for the superfine mode in standard procedure. On the other hand, facsimile machines manufactured under previous ITU-T Recommendation and already used in offices and homes do not understand a newly added functional bit since such a functional bit should be included in a protocol signal for the non-standard procedure under old ITU-T Recommendation.
Therefore, two facsimile machines manufactured under new ITU-T Recommendation can communicate with each other. Also, a facsimile machine of old ITU-T Recommendation and that of new ITU-T Recommendation can communicate with each other. But, even if a functional bit for the superfine mode is sent to a facsimile machine of old ITU-T Recommendation from a facsimile machine of new ITU-T Recommendation, the former cannot understand such a functional bit so that the image data transmission is not conducted in the superfine mode between these two facsimile machines.